Figure 4:

A: Phrenic neurogram showing the effect of glutamatergic disfacilitation of the preBötzinger Complex (preBötC) in one animal. Shown are clips after bilateral injection of NBQX (left) and after subsequent bilateral injection of AP5 (right). There was significant shortening of inspiratory (TI) and expiratory (TE) duration and decrease in peak phrenic amplitude (PPA) until apnea ensued. There was no tonic activity. B1: Phrenic neurogram showing the effect of glutamatergic disfacilitation of the Bötzinger Complex (BötC) and preBötC in a different animal. Shown are clips after bilateral injection of NBQX and AP5 into the BötC, after subsequent bilateral injection of NBQX into the preBötC, after AP5 injection into the left preBötC and after AP5 injection into the right preBötC. TI, TE and PPA significantly decreased until rhythm was lost, however, significant tonic activity persisted. B2: Enlarged detail of the indicated time points. C: To determine whether PPA changed in parallel with respiratory phase timing we plotted the breath-by-breath data for respiratory rate (BPM), TI and TE from the displayed sections in 4A and 4B. Data were smoothed using Lowess function. PPA for BötC injections was calculated as the amplitude of the phasic activity above tonic activity. The decrease in PPA correlated with the change in respiratory phase timing, in particular with TI. As PPA decreased below a certain threshold (red line) regular rhythm was lost. For the pooled data for Protocols 1–3, we averaged only data to the right of the threshold.